15 Instant Messaging Presence

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Petrozavodsk Kimmo Raatikainen September 10, 2004

Instant Messaging and PresenceInstant Messaging and Presence

Kimmo Raatikainen

[email protected]

Petrozavodsk, September 10, 2004 Kimmo Raatikainen 2

LessionLession OutlineOutline

Overview

A Model for Presence and Instant Messaging

Common Profile for Presence

Common Profile for Instant Messaging

SIMPLE

XMPP


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OverviewOverview 1/31/3

Presence and Instant Messaging have recentlyemerged as a new medium of communications overthe Internet.

Presence is a means for finding, retrieving, andsubscribing to changes in the presence information(e.g. "online" or "offline") of other users.

Instant messaging is a means for sending small,simple messages that are delivered immediately toonline users.



Applications of presence and instant messagingcurrently use independent, non-standard and non-interoperable protocols developed by various vendors.

The goal of the IETF IMPP WG is to define a standardprotocol so that independently developed applicationsof instant messaging and/or presence can

interoperate across the Internet.


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It is expected that Presence and Instant Messagingservices will be particularly valuable to users overmobile IP wireless access devices.

Indeed the number of devices connected to theInternet via wireless means is expected to growsubstantially in the coming years.

It is not reasonable to assume that separate protocolswill be available for the wireless portions of theInternet.


A Model for Presence andA Model for Presence andInstant MessagingInstant Messaging

RFC 2778


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OverviewOverview

The model consists of a number of named entities that appear, in

some form, in existing systems.

The model defines two services: a Presence Serviceand an

Instant Message Service.

The Presence Serviceserves to accept information, store it, and

distribute it.

The information stored is Presence Information.

The Instant Message Serviceserves to accept and deliver

Instant Messagesto Instant Inboxes.


Presence ServicePresence Service

Presence Service

PresentityWatcher

Fetcher Subscriber

Poller


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Presence ServicePresence Service 1/31/3

The Presence Servicehas two distinct sets of "clients".

One set of clients, called Presentities, providesPresence Informationto be stored and distributed.

The other set of clients, called Watchers, receivesPresence Informationfrom the service.



There are two kinds of Watchers, called Fetchersand Subscribers.

A Fetchersimply requests the current value of somePresentity's Presence Informationfrom thePresence Service.

A Subscriberrequests notification from the Presence

Serviceof (future) changes in some Presentity'sPresence Information.

A special kind of Fetcheris one that fetchesinformation on a regular basis: a Poller.


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The Presence Servicealso has WatcherInformationabout Watchersand their activities interms of fetching or subscribing to PresenceInformation.

The Presence Servicemay also distribute WatcherInformationto some Watchers, using the same

mechanisms that are available for distributingPresence Information.

Changes to Presence Informationare distributed to

Subscribersvia Notifications.


Instant Message ServiceInstant Message Service

The Instant Message Servicealso has two distinctsets of "clients":

Sendersand Instant Inboxes.

A Senderprovides Instant Messagesto the InstantMessage Service for delivery.

Each Instant Messageis addressed to a particularInstant Inbox Address, and the Instant Message

Serviceattempts to deliver the message to a

corresponding Instant Inbox.


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ProtocolsProtocols

A Presence Protocoldefines the interaction betweenPresence Service, Presentities, and Watchers.

Presence Informationis carried by the PresenceProtocol.

An Instant Message Protocoldefines the interactionbetween Instant Message Service, Senders, and

Instant Inboxes.

Instant Messagesare carried by the InstantMessage Protocol.


FormatsFormats 1/31/3

The model defines the Presence Informationtoconsist of an arbitrary number of elements: PresenceTuples.

Each such element consists of a Statusmarker, anoptional Communication Address, and optional OtherPresence Markup.


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Common Profile for PresenceCommon Profile for Presence(CPP)(CPP)

draft-ietf-impp-pres-02

February 28, 2003


Subscribe OperationSubscribe Operation

When an application wants to subscriber to thepresence information associated with a Presentity, itinvokes the subscribeoperation.

The subscribe operation has the following attributes:

watcher, target, duration, SubscriptID and TransID.

The 'watcher' and 'target' identify the Watcherand

Presentity, respectively.


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Response OperationResponse Operation

Upon receiving a subscribe operation, the serviceimmediately responds by invoking the responseoperation containing the same TransID.

The response operation has the following attributes:

status, TransID, and duration.

'status' indicates whether the subscribe operation has

succeeded or failed.

The 'duration' attribute specifies the number of seconds for

which the subscription will be active.


Notify OperationNotify Operation

If the response operation indicates success, theservice immediately invokes the notifyoperation tocommunicate the presence information to theWatcher.

The notify operation has the following attributes:

watcher, target, and TransID.

The values of 'watcher' and 'target' are identical to those

given in the subscribe operation that triggered this notify

operation.

The TransID is a unique identifier for this notification.


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UnsunscribeUnsunscribe

The application may prematurely cancel a subscriptionby re-invoking the subscribe operation (as describedabove) with a duration of 0 and the same SubscriptIDas the original subscribe operation

Note that a notify operation will be invoked when asubscription is prematurely canceled in this fashion;

this notification may be discarded by the watcher.


Common Profile for InstantCommon Profile for InstantMessaging (CPIM)Messaging (CPIM)

draft-ietf-impp-im-02

February 28, 2003


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Message OperationMessage Operation 1/21/2

When an application wants to send a message to anInstant Inbox, it invokes the messageoperation,

The message operation has the following attributes:

source, destination, MaxForwards and TransID.

'source' and 'destination' identify the originator and recipient

of an instant message, respectively, and consist of an

Instant Inboxidentifier.

The MaxForwards is a hop counter to avoid loops through

gateways. Its initial value is set by the originator.


Message OperationMessage Operation 2/22/2

The TransID is a unique identifier used to correlate message

operations to response operations; gateways should be

capable of handling TransIDs up to 40 bytes in length.

The message operation also has some content, theinstant message itself, which may be textual, or whichmay consist of other data.

The specification assumes that instant messagingprotocols provide reliable message delivery:

there are no application-layer message delivery assurance

provisions in this specification.


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Response OperationResponse Operation

Upon receiving a message operation, the serviceimmediately responds by invoking the responseoperation containing the same transaction-identifier.

The response operation contains the followingattributes:

TransID and status.

The TransID is used to correlate the response to a particular

instant message.

Status indicates whether the delivery of the message

succeeded or failed.


SIMPLE: SIP for InstantSIMPLE: SIP for InstantMessaging and PresenceMessaging and Presence

IETF WG


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SIP as a Presence ProtocolSIP as a Presence Protocol

This is accomplished through a concrete instantiationof the general event notification framework defined forSIP, and as such, makes use of the SubscribeandNotifymethods defined there.

SIP is particularly well suited as a presence protocol.

SIP location services already contain presence

information, in the form of registrations.


Event PackageEvent Package

This event package is based on the concept of apresence agent, which is a new logical entity that iscapable of accepting subscriptions, storingsubscription state, and generating notifications whenthere are changes in presence.

This event package is also compliant with the

Common Presence Profile (CPP) framework.


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Presence User Agent (PUA)Presence User Agent (PUA)

A Presence User Agent manipulates presenceinformation for a presentity.

Multiple PUAs per presentity are allowed.

This means that a user can have many devices, eachof which is independently generating a component ofthe overall presence information for a presentity.

PUAs push data into the presence system, but areoutside of it, in that they do not receive SUBSCRIBEmessages, or send NOTIFY messages.


Presence Agent (PA)Presence Agent (PA) 1/21/2

A presence agent is a SIP user agent which iscapable of receiving SUBSCRIBE requests,responding to them, and generating notifications ofchanges in presence state.

A presence agent must have knowledge of thepresence state of a presentity.

This means that it must have access to presence datamanipulated byPUAs for the presentity.


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Presence Agent (PA)Presence Agent (PA) 2/22/2

A PA is always addressable with a SIP URI thatuniquely identifies the presentity:

sip:[email protected]

There can be multiple PAs for a particular presentity,each of which handles some subset of the totalsubscriptions currently active for the presentity.

A PA is also a notifier (RFC 3265) that supports the

presence event package.


Presence ServerPresence Server

A presence server is a physical entity that can act aseither a presence agent or as a proxy server forSUBSCRIBE requests.

When acting as a PA, it is aware of the presenceinformation of the presentity through some protocolmeans.

When acting as a proxy, the SUBSCRIBE requestsare proxied to another entity that may act as a PA.


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Edge Presence ServerEdge Presence Server

An edge presence server is a presence agent that isco-located with a PUA.

It is aware of the presence information of the presentitybecause it is co-located with the entity that manipulatesthis presence information.


Extensible Messaging andExtensible Messaging andPresence ProtocolPresence Protocol

IETF XMPP WG


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XMPP CoreXMPP Core

The Extensible Messaging and Presence Protocol(XMPP) is an open XML protocol for near-real-timemessaging, presence, and request-response services.


ServerServer

A server acts as an intelligent abstraction layer for XMPP

communications.

Its primary responsibilities are to manage connections from or

sessions for other entities and to route appropriately-addressed

XML data "stanzas" among such entities over XML streams.

Most XMPP-compliant servers also assume responsibility for the

storage of data that is used by clients.

Compliant server implementations MUST ensure in-order

processing of XML stanzas received from connected clients,

servers, and services.


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ClientClient

Most clients connect directly to a server over a TCP socket and

use XMPP to take full advantage of the functionality provided by

a server and any associated services.

Multiple resources (e.g., devices or locations) MAY connect

simultaneously to a server on behalf of each authorized client

with each resource connecting over a discrete TCP socket

and differentiated by the resource identifier of a JID

The port registered with the IANA for connections between a

Jabber client and a Jabber server is 5222.


GatewayGateway

A gateway is a special-purpose server-side servicewhose primary function is to translate XMPP into theprotocol(s) of another messaging system, as well as totranslate the return data back into XMPP.

Examples are gateways to SIMPLE, Internet RelayChat (IRC), Short Message Service (SMS), SMTP,

and foreign instant messaging networks such asYahoo!, MSN, ICQ, and AIM.

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